Supported element types

Radiating elements may be defined with 1 to 4 corner nodes. The elements may be linear or parabolic.

  • A 1-node element is a sphere, with a defined surface area.

  • A 2-node element is a circular cylinder, with a defined surface area per unit length when used as a beam. For the edge of an axisymmetric 2D element, a 2-node element represents a segment of a ring with a defined surface area based on its radius and length.

  • A 3 or 4-node element must be planar, unless it is a parabolic element. Its surface normal orientation is defined by the ordering of its nodes. If the nodes are seen in a counterclockwise order, the element faces the viewer.

To model the reverse side of a planar element, you must create a separate element with, or define the reverse side properties.

If an element has midside nodes defined, it will be considered as a parabolic element. During ray-tracing calculations, the curvature of the parabolic elements is considered when calculating the point of interception and the direction of the reflected rays.

Only elements with positive or zero emissivities take part in radiation calculations. Solid elements are not recognized by the thermal solver for view factor calculation.

  • An element may be flagged as non-radiating, in which case it is ignored for radiative calculations, but is recognized for thermal coupling calculations, even for creating radiative thermal couplings.

  • An element may be flagged as non-shadowing, in which case it will not shadow other elements during radiation calculations.

  • An element may be flagged as non-emitting, in which case neither it nor its reverse side can emit radiation or shadow radiation calculations.

  • Elements with negative solar absorptivity values are not recognized for solar view factor, planet view factor, or albedo view factor calculations.

Circular elements

If an element is specified as circular, the solver approximates the circular shape of the surface by creating a number of internal flat elements. The nodes of these internally generated elements facet the surface of the circular element.

For user-defined circular elements that subtend angles less than 135 degrees from the center of the circle, internal elements are created such that each one subtends an angle of no greater than 45 degrees. If the user-defined circular element subtends an angle greater than 135 degrees from the center of the circle, it is subdivided into 4 elements.

The view factors and areas of the internal elements are merged to create the view factor for the circular element.

Axisymmetric Elements

If an element is specified to be axisymmetric, it lies in the XZ plane. To allow the calculation of 3D radiative phenomena, N planar elements rotated about the global X, Y, or Z axis are created internally in the thermal solver for each profile element defined on the relevant plane. N defaults to 8. The N elements' view factors and areas are merged by the solver.

Warpage angle

Each linear quadrilateral element has a warpage angle calculated, which is the degree of departure from planarity of the element's surface. If the element's warpage angle is greater than 0.1 degrees, it is flagged as warped. Warped elements are treated differently in a number of different procedures. It is not recommended for a model to have warped linear elements. Should the effects of element curvature be desired for ray-tracing calculations, parabolic elements should be used.